In recent years, since the exploration technique and extractive technique for oil fields and gas fields are improved, it is not uncommon to produce oil from oil fields at a depth of thousands meters. An enormous number of oil well pipes are used in such oil wells, and each oil well pipe maintains seal property by means of a threaded joint and the oil well pipes are connected into one so as to be used.
Japanese Patent Application Laid-Open No. H06-99354 discloses a technique in which a metal-to-metal seal part of a steel pipe joint is subject to the shot peening treatment in order to improve galling resistance by means of heightening of surface hardness. Further, Japanese Patent Application Laid-Open No. H08-145248 discloses a technique in which the hardness of a male or female threaded seal part is heightened and surface roughness of the threaded seal part with the heightened hardness is prescribed to 0.25 to 1.00 μm so that the galling resistance of high-chrome steel containing Cr of 10% or more in weight ratio is improved.